US2425909A - Method of controlling thread tension - Google Patents

Description

Au@- 39 1947 K. E. WILHELM 2,425,909

METHOD OF CONTHOLLING THREAD TENSION Filed Dec. 14, 1945 3 Sheets-Sheet 1 K. E. WILHELM METHOD 0F CONTROLLING THREAD TENSION Filed D. 14, 1945 3 Sheets-Sheet 2 Aug., 19, 1947. K. E. WILHELM 2,425,909

METHOD 0F CONTROLLING THREAD TENSION Filed Dec. 14, 1945 3 Sheets-Sheet 3 Patented ug. 19, 1947 METHOD F CONTROLLING THREAD TENSION Kurt E. Wilhelm, Providence, R. I., assignor to United States` Rubber Company, New York, N. Y., a corporation of New Jersey Application December '14, 1945, Serial No. 635,072

7 Claims. (Cl. 242-45.)

This invention relates to a novel method of controlling the tension of a thread or strand during a winding operation to thereby keep the pounds per square inch tension of the thread constant. The present method is particularlyl well adapted to control the tension of a rubber thread as it is wound on a golf ball, but may be used for tensioning threads for other purposes.

Golf balls as usually constructed consist of a core about Which a rubber thread or tape is wound under considerable tension to form the ball body that is later provided with a protecting cover.

The better golf balls are wound under high tension since the higher the tension with which the rubber thread is wound the greater will be the flight of the ball.

Various types of tension devices have been employed heretofore to control the tension of the rubber thread as it is-supplied to a golf ball and many of' these tension devices operatel automatically to maintain a constant pull upon the thread being wound on the ball.

That is such prior tension devices exert Ya constant pull on the running thread regardless of thread size variations, and as a result when the thread runs small the rubber forming the same will be stretched to a greater degree than normal and when the thread runs large it will be stretched to a less degree than normal.

The rubber threads available for winding golf balls do not run uniform as to size even When carefully manufactured, and when such a thread is subjected to a constant tensioning pull as heretofore, regardless of thread size variations, the rubber forming the portions of the thread that are undersize will be stretched to amuch greater degree than the rubber forming the portions of the thread that are oversized. This results in a substantial variation in the degree of'stretch of the rubber thread wound upon the ball and a corresponding variation in the density of the balls. It will therefore be seen that noy matter how well a golf ball tension device may operate to exert a predetermined constant pull upon a thread, any variation in the size of the running thread will cause variations in the degree to which the thread is stretchedY as `it lies on the ball. This in turnwill produce variations in the density and ght propertiesof the balls.

Heretofore in winding the better grade golf balls'it has been the usual practice to select the permissible thread gauge tolerance such as 10% variation in the size of the rubber thread and then measure the thread from time to time to see erties.

if its size is within the tolerance range. This involves considerable timeY and expense but was necessary to keep the density of the nished golf balls within a selected range. The present invention makes this prior'practice unnecessary since wide variations in the size of thethread being wound will not affect the density of the finished ball as will now be explained.

The primary purpose of the present invention is to produce golf. balls that will possess a high degree of uniformity as to density and ight prop- To accomplish this'the present invention employs an entirely different principle from that used heretofore to control the tension of the thread for golf balls, in that in accordance with the present invention the thread lis supplied to the golf ball under constant pounds per square inch winding tension and not under a constant pull as heretofore.' Stated differently the aim of the presentinvention is to keep the poundsper square inch tension of the thread constant independently of size variations' in the running thread. Y

The operation of the present invention is such that the actual tension exerted upon the thread at any instant is controlled in accordancewith the crossV sectional area of the particular portion of the thread being wound at that instant. If this portion of the thread is undersized the total pull being exerted on the thread at such instant will be reduced whereas if the cross sectional area of thethread is oversized the total pull will be increased, so that the poundsper square inch tension oi the rubber thread will be maintained constant throughout a Wide range of size variations in the thread.

The method contemplated by the present invention .for controlling'the pounds per square inch tension of a running thread operates quickly to make corrections for variations inthe size ofthe thread. That is the electrical control used will make a correction in an `extremely small fracl tion of a second and before the tensioned thread, when being wound at high speed, will travel one f foot after a change in the rate of thread vibration occurs. This accurate control of the tension of the thread as its size varies produces golf balls of uniform playing properties, and reduces the likelihood of the thread breakingduring the ball winding operation.

In carrying out the present invention Vthe thread which is being wound upon a golf ball is drawn forwardrbythe ball under tension so that it passes over two spaced points, and the length of thread extending between thesepoints is kept of the running thread vibrating at its natural strand or filament that is being wound upon a spool or other package, but is particularly well adapted for use in controlling the tension of a rubber or elastic thread which is being wound. The thread tensioning mechanism contemplated by the present invention may be used upon various types of golf ball winding machines and is frequency. A second step employs means for detecting the frequency at which the thread is vibrating at each instance. A third step employs electronic means fo;` automatically varying the total tension applied to the thread in accordance with the variations in such frequency, to thereby keep the frequency at which the thread vibrates practically constant irrespective of size variations in the running thread.

One good practicalmeans for keeping the running thread vibrating resides in two small jets Vof air disposed at right angles to each other and to the thread so that they strike the thread and cause it to revolve or vibrate in a somewhat elliptical path.

The means disclosed for continuously determining the rate at which such thread is vibrating resides in a beam fv light which is positioned so that the vibrating thread will move across and interrupt this light beam, and at the opposite side of the thread from the light source is placed a light sensitive device capable of detecting the interruption of the light beam each time it is cut by the vibrating thread. In this way the beam is modulated at twice the frequency of thread vibration.

This modulated light beam is used to control electronic means which operates to increase or decrease the applied tension upon the thread in accordance with the rate at which the thread is vibrating, to thereby keep the frequency at which the thread vibrates as nearly constant as possible. By keeping this rate of vibration constant as variations in the size of the thread occur the pounds per square inch tension of the thread will be kept constant and this will produce balls of uniform density. Y

. The various features of the method of the present invention will be more fully understood from the following description when read in connection with the accompanying drawings where- Fig. 1 is an end View, with parts broken away, of a golf ball winding machine having associated therewith the tension controlmechanism contemplated by the present invention.

Fig. 2 is a front elevation of the tension control mechanism andv supporting cabinet shown in Fig. l.

Fig. 3 is a top plan view of Fig. 1.

Fig. 4 on a larger scale shows mechanism for vibrating the thread traveling between space points.

Fig. 5 is a sectional View taken on line 5-5 of Fig. 2.

Fig. 6 is a rear View of the interior of the cabinet showing the solenoids and associated parts to be described: and

Fig. 7 is an electrical diagram of mechanism for varying the tension upon the thread when its rate of vibration changes.

The present invention may be employed to control automatically the tension of a thread,

shown as associated with a golf ball winding machine of the general type disclosed in the Cobb Patent No. 1,270,009.

The winding machine shown in the drawings comprises a metal casing I0 mounted upon a frame I I adapted to support the winding machine at the desired distance from the floor. The casing I 0 is formed with the housings I2 and I3 which are spaced apart to provide therebetween the opening in which the ball supporting heads I4 and I5 operate. These heads are supported and rotated by axially aligned shafts I6 that are mounted for limited longitudinal movement to facilitate the introduction of a ball B between the heads and an increase in the size of the ball as the thread is wound thereupon. The heads I4 and I5 rotate at the same speed and turn the ball upon the longitudinal axis of the shafts I6 to wind the thread in a plane extending through the center of the ball at right angles to said longitudinal axis. The ball is actually supported by the discs I1 providedupon the heads I4 and I5 and these discs are periodically rotated relatively to the heads to turn the ball and distribute the windings uniformly over its surface, as more fully explained in said patent.

In the construction shown a cabinet I8 adapted to support or house the thread tension means is secured in front of the golf ball winding inachine. The rubber thread T is supplied to the golf ball B under tension from a spool I9 supported in front of the cabinet I8, as will be apparent from Fig, 1. This threadl is led upwardly from a supply spool I9 to and around a, thread tension drum 20 and then upwardly over a first grooved wheel 2I, where it travels horizontally to a second grooved wheel 22 to -pass downwardly therefrom in an inclined .direction to the ball B. Y

The parts I9 to 22 inclusive are shown in the drawings as supported by the metal cabinet I8 which is rigidly secured in front of the winding machine casing I0 and serves to house electrical and mechanical apparatus to be described.

The thread spool I9 is supported by a bracket 23 attached to the front of the cabinet I8 and having the spaced laterally extending arms 24 which rotatably support the spool I9 and also support the roller 25 about which the thread T `pases before it travels upwardly to the rum 20.

The bracket 23 preferably has pivotally secured thereto'a weight 26 adapter to rest upon a flange of the spool-I9 to apply an initial tension to the thread T and prevent the spool from over-running when the winding machine is stopped.

The thread tensioning drum 20 is shown as supported by spaced brackets 2'I secured to the front of the cabinet I8 and adapted rotably to support the shaft 28 to which the drum 2D is rigidly secured. This shaft also has rigidly secured thereto a brake drum 29 which is engaged by the brake band 30. One end of this band 1s anchored to a pin 3I secured to the bracket 27 and the other end has secured thereto a spring 32, turn buckle 33 and threaded bolt 34. rihis bolt extends into the cabinet I8 and through a hole in the block 35 and has mounted on its protruding' end a threaded pulley 36. The arrangement is such that rotation of this pulleyin one direction will tighten the brake band 30 about its drum 29 and rotation of this pulley'in the opposite direction will lessen the tension upon this brake band. The cabinet I8 has mounted upon its lupper end the boxes 31 that are spaced from each other to provide an opening in which there is mounted a horizontally extending beam 38 adapted rotatably `to support at its opposite end the grooved wheels 2I and 22.

It will be understood from the mechanism so far described that when the golf ball winding machine is operated by driving the heads I4 and I5 to rotate the ball B the thread T will be un'- wound from the spool IS to pass'around the roller 25 and then upwardly to the drum 20 about which it is looped one or more times, and then passes over the spaced grooved wheels 2I and 22 and to 5 the golf ball.

be controlled :by rotating the threaded pulley 36 to thereby control the tension of the brake band. 30. Rotation of the pulley 36 is secured in the construction shown by looping around this pulley several times a`-newire 39 so that one end portion of this wire extends laterally and then downwardly about a grooved pulley 69, and the other end portion extends laterally in the opposite direction and then downwardly about the grooved pulley 4 I. The arrangement is such that a downward pull upon one end of this wire will rotate the pulley 36 in one direction and a downward pull at the other end of this wire will rotate the pulley in the opposite'direction. The means shown for exerting a downward pull upon the opposite ends of the wire 39 and for operating this wire to rotate the pulley 3B and thereby control the tension of the thread T comprises the solenoids 42 and 43 mounted within the cabinet I8. Onev of these solenoids has mounted therein the sliding iron core 44 secured to one end of the wire 39 and the other solenoid has the core 45 secured to the other end of this wire. Both solenoids are made relatively long so that each core may travel a substantial distance within its solenoid under the inuence of the magnetic:

eld produced by the solenoid, to thereby turn the threaded pulley 3B through a sufficient number of revolutions to control the tension upon the brake `band 30 throughout the desired range. The cores 44 and 45 extend downwardly a substantial distance beyond the lower ends of their respective solenoids to enter the dash pots 46 containing a liquid, or a gas such as air, to Lict upon the disc 41 at the lower end of each core to prevent these cores from moving too rapidly. The arrangement is such that the weight of these cores will keep the wire 39 under tension and when one core is raised as a.result of its solenoid becoming excited, the other core will move downwardly under the influence of gravity. In this way a very simple and effective means is provided for automatically controlling the brake action upon the brake drum 29.

In carrying out the method of the vpresent invention that portion of the thread 'I' which ,is advancing between the spaced rollers 2|l 22 is caused to vibrate at itsrnatural frequency, and means is provided for automatically detecting the rate at which this thread is vibrating, and also for automatically controlling the tension upon the thread T so as to keep its frequency' of vibration practically constant as variations in the size of the thread occur. The solenoids 42 and 43 and' associated mechanism above described It will also be understood that the amount of tension placed upon this thread can will automatically control the tension upon the thread 'I' provided the operating current supplied to these solenoids is properly controlled. The length of the thread T extending between the spaced rollers 2I, 22 is conveniently kept vibrating by pipes 48 and 49 disposed at right angles to each other as shown in Fig. 4 and adapted to direct jets of air against the tensioned thread so that the jet 'of air from the pipe lIll-will force the stretched thread, upwardly, whereupon vthe `jet from the pipe 4S will force the thread laterally slightly out of the path of the jet 48 so that the thread may vibrate more easily in a downward direction. In this manner the thread iskept V.vibrating by revolving in a somewhat elliptical terruptthis beam upon Veach up and down stroke of its vibration.

IThis is accomplished in theconstruction shown by mounting above the cabinet I8 in kone of the boxes 31 an electric light 50 which preferably contains a single straight vline filament, and mounted within this same box half way between the vibrating rubber vthread T and light 50 a lens 5i positioned so that the image 'of thev lament 5i) will fall upon the thread when the latter occupies a mid stroke straight line position. `The effect of this is to `cause the thread T to interrupt the beam of light on each up and down stroke of its vibration, and at the instant s uch light beam is'interrupted it-will Vfail to fall upon the phototube 52 mounted in the otlierbox 31 at the opposite side of the thread from 'the light 5U. The construction of the boxes 31 is such that all external light is excluded therefrom except the small amount that may enter through small holes formed inthe adjacent vertical 'walls of these boxes to clear'the light beam.

The light 5D may be supplied with an operating current from any suitable source. The photo- 4tube 52 is ineludedfin the electric circuit shown in Fig. '7 wherein there is'illustrated an electrical assembly diagram that is formed of the three separate diagramsl marked A, B and C. The operation of-this electricalapparatus -will now be described.

The light falling on the photo-tube 52 will be interrupted at twice the frequency of the thread vibration. This will cause a varying current through this tube, and hence a varying voltage drop across the resistor53 is generated. This varying voltage, which may be called the signal voltage, is applied through the blockingcondenser 54, and across the grid resistor 55', to the grid of the triode 56. x

vIt will be noted that diagram A employs the three stage transformer coupled amplifier using the triodes 56, 51 and 58. The purpose in providing this construction is to amplify the signal voltage and provide suicient power to`operate the remainder of the apparatus. Also this three stage amplifier is designed to change the signal voltage into a sinusoidal form. 'I'his is accomplished sufliciently well, for applicants purpose, by the use of unbypassed cathode resistors 59, 60 and 6I and transformers 62, 63 and 64 in the plate circuits. In the case of the rst stage which employs the triode 56, the eiect isenhanced by the use of the additional resistor 65 in the cathode circuits. The resistor 6E and condenser 61 are used in order to maintain the proper grid bias.

The detector circuit is shown in diagram B, wherein by employing the transformers 68 and 69 the amplified and modified signal voltage is applied to the plates of the triodes and 1l respectively. The polarities of these triodes are such that the phase difference between the voltages applied is 180.

The transformer 12 of this diagram B feeds the signal voltage to the grids of the triodes 10 and 1|. A condenser 13 is provided to shift the phase 90. In order to accomplish this its impedance at the operating frequencies is made large compared to the impedance of the resonant circuit 14 which includes the coil 15 and condenser 1B. It is important to understand that the circuit 14 has a selected or established resonance frequency, such as 1000 Vibrations per second, built into the circuit. Thus, if the frequency of the signal voltage. is equal to the selected resonancel frequency of the circuit 14 the voltage applied to the grids 10 and 1l will be 90 out of phase with the signal voltage. At the selected resonance frequency, there will be no phase shift across the resonant circuit 14. Under these conditions, the plate voltage of one tube will lead the voltage upon the grid by 90 while the plate voltage of the other tube will lag the grid voltage by 90. The magnitude of the grid voltage is made so large that the voltage at the grid is essentially either negative beyoud the eut-off veine or else siighuy positive. The resistors 11 and 18 serve to keep the positive values small, Therefore, if the frequency of the signal voltage is equal to the resonant frequency of circuit 14, the average current through 10 and 1I will be equal to each other. It will be understood that the actual magnitude of the grid voltage, provided it is made large enough, will not materially affect the results.

. If in this diagram B the signal frequency is larger or smaller than the resonance frequency of the circuit 14 the phase across such circuit will change in one direction or the other, so ,that the grid voltage will get more into phase with the plate voltage of one tube and more out of phase with the plate voltage of the other tube. Thus the average current through one of these tubes will increase and that through the other will decrease. The voltage drop across resistors 19 and 80 will, as a result, be correspondingly di1erent,.it being understood that the effect of changes in the magnitude of the grid voltage is negligible. A condenser 8l serves to keep the detecting circuit at ground rpotential as far as alternating currents are concerned.

Resistors 82 and 83 of Diagram C are employed so that whatever difference in voltage is developed across resistors 19 and 80 it will be applied in an equal, though oppositein sign, manner to the grids of the beam power tetrodes 84 and 85. Resistors 86 and 81, and condensers 88 and 89 comprise the filter net work that prevents voltage variations at the frequency of the signal Voltage from reaching the grids of tetrodes 84 and 85, while at the same time they still permit corrections to take place in a small fraction of a second. Resistor 90 is a cathode bias resistor for tetrodes 84 and 85,

As long as the voltages of the grids of tetrodes 84 and 85 are equal, which is the case when the signal frequency is the same as a resonant frequency of circuit 14 or when there is no signal voltage at all, the plate currents of tetrodes 84 and 85 and hence the pulls on the movable iron cores 44' and 45 in the solenoids 42 and'43 will be equal. I! the signal frequency is different on the tetrodes 84 and 85 will not be equal, and

the pull on the iron cores 44 and 45 will not be the same. Under these conditions the cores will move in such a way as to adjust the tension on the thread T so as to cause it to vibrate at the selected frequency, `and thereby produce the desired pounds per square inch tension in the thread. It will be understood that the movement of the iron cores takes place until the desired pounds per square inch tension is obtained. When the pulls exerted by the solenoids on the cores are equal no motion will take place.

The resistors 53 and 55, where the signal voltage is slight, may be of the order of one or two megohms, and as the signal voltage is built up as it advances to diagrams B and C resistors of greater current carrying capacity .will be used. The electrical or electronic mechanism of Fig. '1 may be housed in the metal cabinet I8 and the grounds shown in Fig. '7 may be formed by grounding these points to this metal cabinet. Operating current is supplied to the diagrams A, B and C at the points indicated.

The relationship between the frequency of thread vibration and pounds per square inch tension is shown by the following formula:

where But M :Ad

where A=crosssectional area of thread dzvolume density Substituting in the first formula above where S=pounds per square inch tensio'n Stating this in words we have, for a given distance L and a given volume density d the natural frequency ofA vibration is proportional to the square root of the pounds per square inch tension.v Applying this information to the problem at hand is found that a selected number of thread Vibrations per second will produce a ball of a particular density. The apparatus disclosed operates to change the thread tension as necessary to keep its rate of vibration constant.

The present method makes permissible Variations in the size of the rubber thread being wound on a golf ball through a range of 25% or more, since such variations in the size of the running thread will not vary the density of the wound ball, and by securing uniform density all balls of a particular grade will play the same.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. The method of controlling the tension of a thread, which consists in advancing the thread under tension past two fixed points and vibrating the portion of the thread traveling between these points at its natural frequency, automatically detecting the rate of thread vibration, and

automatically varying the tension upon the thread so as to keep its frequency of vibration practically constant as variations in the size of the thread occur. to thereby keep the pounds per square inch tension of the thread constant.

2. The method of controlling the tension of a thread, which consists in advancing the thread under tension past two fixed points and vibrating the portion of the thread-traveling Ibetween these points at its natural frequency, electrically detecting the rate of thread vibration, and automatically varying the tension upon the thread so as to keep its frequency of vibration practically constant as variations in the size of the thread occur, to thereby keep the pounds per square inch tension of the thread constant.

3. The method of controlling the tension of a thread, which consists in advancing the thread under tension past two i'lxed points, vibrating by means of air the portion of the thread traveling between these points at its natural frequency, automatically detecting the rate of thread vibration, and automatically varying the tension upon the thread so as to keep its frequency of vibration practically constant as variations in the size of the thread occur, to thereby keep the pounds per square inch tension of the thread constant.

4. The method of controlling the tension of a thread, which consists in advancing the thread under tension past two fixed points and vibrating the portion of the thread traveling between these points at its natural frequency, producing an electrical signal frequency that bears a definite relation to the frequency of thread vibration and utilizing said signal frequency to control the tension on the thread so as to keep its frequency of vibration practically constant as variations in the size of the thread occur, to thereby keep the pounds per square inch tension of the thread constant.

5. The method of controlling the tension of a thread, which consists in advancing the thread under tension past two fixed points and vibrating the portion of lthe thread traveling between these points at its natural frequency, utilizing a beam of light to detect the rate of thread vibration and produce signals of a corresponding frequency, and varying the tension upon the thread in accordance with the signal frequency so as to keep the frequency of thread vibration practically constant as variations in the size of the thread occur, to thereby keep the pounds per square inch tension of the thread constant.

6. The method of controlling the tension of a thread, which consists in advancing the thread under tension past two fixed points and vibrating the portion of the thread traveling between these points at its natural frequency, automatically detecting the rate of thread vibration and producing a corresponding electrical signal, establishing a related circuit having a xed resonant frequency, and automatically varying the thread tension to keep the signal frequency the same as that of the resonant frequency, to therelby keep the pounds per square inch tension of the thread constant.

7. The method of producing golf balls of uni-t form density, which consists in winding each ball with an elastic thread under tension past two fixed points, keeping the portion of the thread traveling between these points vibrating at its natural frequency, electrically detecting the rate of thread vibration and controlling by electrical means the tension upon the thread so as to keep its frequency of vibration practically constant as variations in the size of the thread occur, to thereby wind a ball so that its density is uniform although the size of the thread varies.

KURT E. WILI-IELM.

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